An image forming process using the electrographic technique is widely adapted in image forming apparatus, such as photocopy machines, facsimile machines and printers. In the electrographic technique, a direct transfer technique and an intermediate transfer technique are known as methods to transfer a developer image onto a recording medium (hereinafter also referred to as “medium”), such as sheet and the like. The direct transfer technique is a technique to transfer the developer image formed directly on a photosensitive body onto a medium. In contrast, the intermediate transfer technique is a technique to transfer (secondary transfer) the a developer image from an intermediate transfer body onto a medium after once transferring (primary transfer) the developer image formed on a photosensitive body onto the intermediate transfer body. In the case of forming a color image in accordance with the intermediate transfer technique, a process is executed in which developer images of a plurality of colors (e.g., yellow, magenta, cyan and black) are transferred and superimposed on an intermediate transfer body and are subsequently transferred onto a medium.
JP Laid-Open Patent Application No. 2010-277038 and JP Laid-Open Patent Application No. 2001-134041 are examples of prior art documents related to the intermediate transfer technique.
For the intermediate transfer technique, accurate positioning of the developer image on the intermediate transfer body and the medium being carried is required. However, a change in the size of the intermediate transfer body or the occurrence of displacement of the intermediate transfer body inside the image forming apparatus during the operation of the image forming apparatus, for example, often causes the accuracy in positioning the developer image on the intermediate transfer body and the medium to decrease.
In view of the above-described problems, an object of the present invention is to provide an image forming apparatus that improves the accuracy in positioning the developer image on the intermediate transfer body and the medium.